This invention relates to olefin polymerization catalysts and more particularly to improved catalysts for the polymerization of propylene and higher alpha-olefins.
Olefin polymerization catalysts based on transition metal compounds and aluminum alkyls are well known in the art. Particularly, the use of titanium trihalide compounds to produce crystalline propylene polymers has been reported widely. Among recently published catalytic systems based on titanium trihalides are U.S. Pat. Nos. 3,984,350; 4,210,738; 4,210,729; 4,210,736; 4,295,991; 4,182,691 and 4,183,826; all of these references are incorporated herein by reference.
U.S. Pat. No. 4,210,738 describes a titanium halide-based catalyst in the delta crystalline form and having a color tending toward violet made by reducing titanium tetrachloride with an aluminum alkyl, treating the reduced solid with an ether, thioether or thiol complexing agent and reacting with additional titanium tetrachloride.
U.S. Pat. No. 4,210,729 describes a method to preactivate the catalyst described in U.S. Pat. No. 4,210,738 with a metal organic compound of Groups IA, IIA, IIB, or IIIA.
U.S. Pat. No. 4,210,736 describes catalysts such as those listed in U.S. Pat. No. 4,210,738 which have been dried.
U.S. Pat. No. 3,984,350 describes a highly catalytically active titanium trihalide composition in the beta crystalline form having a brown color formed by reducing titanium tetrachloride with an aluminum alkyl and reacting, under controlled conditions, the resulting reduced product with a complexing agent and additional titanium tetrachloride.
U.S. Pat. No. 4,295,991 describes a method to treat a catalyst such as described in the above-cited U.S. patents with olefin monomer such that the resulting catalyst particle is non-friable. The method disclosed in this patent comprises contacting a reduced titanium trihalide composition with olefin monomer, such as propylene, before reacting with a Lewis base complexing agent and either titanium tetrachloride or a chlorinated hydrocarbon.
U.S. Pat. Nos. 4,182,691 and 4,183,826 describe a titanium trichloride catalyst component prepared by reducing titanium tetrachloride with an organoaluminum compound and contacting the reduced solids with a chlorinated hydrocarbon and an aliphatic ether complexing agent.
U.S. patent application Ser. No. 196,012 filed Oct. 10, 1980 and now U.S. Pat. No. 4,324,693, assigned to a common assignee and incorporated by reference herein, discloses an improved olefin polymerization catalyst component prepared by reducing titanium tetrachloride with an aluminum alkyl, contacting the resulting reduced solid with a pretreatment amount of alpha-olefin monomer under polymerization conditions and reacting the resulting product with a Lewis base complexing agent in a molar ratio to the reduced titanium compound of greater than 1.15 to 1 and additional titanium tetrachloride. In addition, a mixed Lewis base complexing agent comprising isoamyl ether and n-butyl ether was found advantageous.
U.S. patent application Ser. No. 297,272 filed Aug. 28, 1981 and now U.S. Pat. No. 4,440,494, assigned to a common assignee and incorporated by reference herein, discloses an improved olefin polymerization catalyst in which the titanium-containing component is an ether-complexed, titanium tetrachloride or chlorocarbon-activated and reduced titanium halide and in which the halogen/aluminum atomic ratio of an aluminum alkyl halide component is between 0.89 and 0.98.
There are many examples of treatment of titanium-containing olefin polymerization catalysts with silicon tetrachloride such as U.S. Pat. Nos. 3,833,515, 3,992,322, 4,022,958, 4,098,907, 4,149,990, and 4,158,988; German Offen. No. 2,111,455 (Chem. Abst. 78: 16788j). Japanese Kokai No. 98,076/77 (Chem. Abst. 88: 38333r); Japanese Kokai No. 90,389/78 (Chem. Abst. 89: 180621i); Japanese Kokai No. 94,908/80 (Chem. Abst. 93: 221319h); and Japanese Kokai No. 73,707/80 (Chem. Abst. 93: 150909n). Other references also describe treatment with chlorosilane (HSiCl.sub.3) such as Japanese Kokai No. 100,986/78 (Chem. Abst. 89: 216061f); Japanese Kokai No. 119,387/79 (Chem. Abst. 92: 42618n); Japanese Kokai No. 138,887/79 (Chem. Abst. 92: 111526v); Japanese Kokai No. 36,203/80 (Chem. Abst. 93: 27105v); Japanese Kokai No. 147,505/80 (Chem. Abst. 94: 122285h); and Japanese Kokai No. 147,506/80 (Chem. Abst. 94: 122287k).
Alkyl-substituted chlorosilanes, such as methyl trichlorosilane, ethyl trichlorosilane, and methyl dichlorosilane have been used to treat various olefin polymerization catalysts such as U.S. Pat. Nos. 3,676,418, 3,875,126, 4,071,672, 4,085,276 and 4,223,117; Japanese Kokai No. 83,284/75 (Chem. Abst. 83: 179954c); Japanese Kokai No. 119,388/79 (Chem. Abst. 92: 7208g); and Japanese Kokai No. 124,888/79 (Chem. Abst. 92: 7211c).
Specific examples of use of alkyl chlorosilanes include U.S. Pat. Nos. 4,159,963 and 4,159,965 which describe a titanium polymerization component obtained by reacting an organomagnesium component with a chlorosilane containing an Si--H bond then reacting the product with a specified titanium compound. The organosilane has a formula EQU HaSiCl.sub.b R.sub.4 -(a+b)
wherein a and b are numbers greater than 0 such that a.ltoreq.2 and a+b.ltoreq.4 and R is a hydrocarbon radical having 1 to 20 carbon atoms. Examples of chlorosilanes included CH.sub.3 SiHCl.sub.2, C.sub.2 H.sub.5 SiHCl.sub.2, n--C.sub.3 H.sub.7 SiHCl.sub.2, C.sub.6 H.sub.5 SiHCl.sub.2 and 4--ClC.sub.6 H.sub.4 SiHCl.sub.2.
U.S. Pat. No. 3,825,524 describes a titanium trichloride composition formed by reacting TiCl.sub.4 with an organoaluminum chloride with a mixed solvent containing an organosilicon compound such as tetrahydrocarbyl silanes, organohydrogensilanes and organohalogensilanes including alkyl trichlorosilanes and alkyl dichlorosilanes.
There is a need for active olefin polymerization catalysts which produce highly crystalline polymer for use in advanced polymerization processes such as gas-phase or bulk processes. The invention disclosed herein produces an active alpha-olefin, especially a propylene, polymerization catalyst, which also produces low amounts of hexane extractables in gas-phase or bulk polymerization processes.